Initially, process control systems and field devices employed to effectuate process control in process plants were generally monitored and controlled in a decentralized fashion. Lacking standardized communication protocols and computing power, closed loop monitoring and control was something left to a plant operator whose situs was generally local to the process plant itself. The need for remote, centralized process control monitoring and control resulted in the development and deployment of field devices employing, for example, the well-known two-wire, 4-20 mA current loop instrumentation and other point to point hard-wired communication systems.
The availability of low cost, low power computing devices fueled the deployment of intelligent field devices equipped with enhanced processing power (microprocessors) and electrical communication abilities. Intelligent field devices could now increasingly communicate (network) with each other, and with centralized process control systems to perform automated control. This improved networking ability translated to enhanced process plant control and consequently, improved process plant output.
With an eye towards improving acceptance of intelligent field devices in the process control industry, and in part to improve intra-operability between these field devices, field device vendors developed and standardized several digital network protocols to allow for inter-process plant field device communication. Some of the standards, the highway addressable remote transducer (HART) protocol for example, were especially appealing because they leveraged the existing analog two-wire, 4-20 mA infrastructure, by now omnipresent on the process plant floor, to transmit and receive digital information between field devices. Other standards included bus based systems, such as the FOUNDATION® Fieldbus standard, the Profibus standard, etc.
Eventually, increasing computing power, increasing component integration and developments in the general field of signal processing made it economically viable to develop and deploy low-range, low-throughput radio frequency (RF) or wireless communication standards for use in the process control industry. Some of these protocols were developed to operate in the unlicensed or loosely-licensed, industrial, scientific and medical (ISM) electromagnetic frequency bands, such as the 2.4 GHz band. Field devices supporting such low-range, low-throughput RF communication protocols in the ISM band were and continue to be deployed in process plant environments. Although unlicensed, governmental agencies may enact regulations that may limit the maximum transmission power. Thus, frequently such protocols are referred to a low power communication protocols. Moreover, several wired network protocols, including the HART protocol for example, were adapted to leverage the wireless capability of such field devices. In particular, the WirelessHART protocol evolved from the wired HART protocol to leverage and allow interoperability of WirelessHART capable field devices within a wired HART process plant network. Notwithstanding these improvements, process plant communication is generally limited to the process plant environments which have very specific robustness and security issues.
However, in a separate industry, and beginning in approximately the 1960s, personal computers have increasingly become commonplace throughout the world. Simultaneously, strides made in the field of general computer networking have lead to the creation of the internet, via which personal computers seamlessly communicate with one another. This seamless communication has in large part been enabled by the acceptance and adherence to the Internet Protocol version 4 (IPv4). The IPv4 protocol, in part, assigns unique IP addresses to computers communicating via a network, and the internet, in general. Failing to anticipate the widespread acceptance of IPv4, the developers of the IPv4 specification constrained the maximum size of the IP address of a computer to 32 bits. However, the proliferation of inter-networked computers, including servers, handheld computers and personal computers has created a situation where IPv4 addresses could run out in the foreseeable future. To preemptively head-off this situation, the newly proposed IPv6 protocol standard, in part, increases the IP address space or length to 128 bits. Mathematically, this translates to 3.4 times 1038 unique IPv6 addresses. In any event, the use of the Internet Protocol (referred to herein generally as IP or the IP network protocol) to perform routing and other communication activities in both wired and wireless environments has become pervasive. In fact, most applications developed today to communicate outside of a device are developed using the Internet Protocol as the backbone of the communications network or to perform networked communications.
Moreover, the needs in the process plant industry are becoming more and more tied to or intertwined with developments being made in general computing technologies. For example, process plants such as refineries, oil fields and mining operations are increasingly being developed in the remotest corners of the globe, close to the site of the raw materials. Increasing globalization has lead to these plants being owned, monitored and controlled by conglomerates located, if not on separate continents, at least in separate countries. Geo-political instability, climatic conditions and/or the unavailability of livable conditions at the site of such process plants have forced corporations to look for means to remotely monitor and control such process plants. While there are many uses of general computer networking advances being used in other types of networked communications, such as cellular telephone, security monitoring applications, etc., existing process control network protocols are ill-equipped and are generally incompatible with general purpose computer network protocols such as IPv4 or IPv6 to allow integration of these protocols within a process plant environment without significant supporting communications infrastructure. In fact, most of the existing process control network protocols were developed independently of, or without regard to now more commonplace or comprehensive general purpose computer protocols, such as the IPv4 or IPv6 communication protocols. Furthermore, the robust security mechanisms available in the general purpose computer protocols, such as 128 bit encryption, have not made their way to the process plant floor network, again limiting the ability to extend the process plant networks outside of controlled plant environments. In fact, most, if not all process plant communication protocols that implement security features are incompatible with the widely employed IPv4 and IPv6 security protocols.
However, with the newly expanded IPv6 address space, it may now be feasible to assign each intelligent field device within a process plant that is capable of communication with an IPv6 address. Thus, it would be extremely advantageous to simply use a general computer networking protocol, such as IPv4 or IPv6, to perform communications within in a plant environment and to make those communications easily extendable to devices outside of the plant. However, not every intelligent field device is or can easily be adapted to conform to or use the IPv4 or the IPv6 protocol, and thus using the IPv4 or IPv6 communication protocols to perform communications and other routing functions within a process plant environment is not currently feasible. In particular, hardware constraints, such as limited field device memory and processing power, makes it technically unfeasible to retrofit existing field devices with software and or hardware complaint with or needed to support the IPv4 or the IPv6 protocol. Similarly, it is not economically feasible to replace every intelligent field device implementing the existing low-power, low-throughput communication protocols implemented in current special purpose networks, such as those encountered on the process plant floor, with an IPv6-enabled field device. As a result, it is currently not feasible or very practical to use the well known, and now ubiquitous, IPv4 or IPv6 protocols to perform communications within or between devices in a process plant, even though many computing devices within a process plant may benefit from being able to run applications that are developed for use in an IPv4 or IPv6 communication protocol environment or to be able to easily communicate with devices outside the process plant network that use such a communication network protocol. As a result, there is a need for field devices that adapted to operate within the legacy wireless process plant networks while at the same time being adapted to communicate with devices located anywhere on the internet.